Standard cell architecture for gate tie-off

ABSTRACT

A chip includes a first gate extended along a second lateral direction, a first source electrically coupled to a power rail, and a first metal interconnect extended along a first lateral direction approximately perpendicular to the second lateral direction, wherein the first metal interconnect lies above the first gate and the first source, and the first metal interconnect is configured to electrically couple the first gate to the first source. The chip also includes a second gate extended along the second lateral direction, a second source electrically coupled to the power rail, and a second metal interconnect extended along the first lateral direction, wherein the second metal interconnect lies above the second gate and second source, the second metal interconnect is configured to electrically couple the second gate to the second source, and the first metal interconnect is aligned with the second metal interconnect in the second lateral direction.

RELATED APPLICATION

The present application is a divisional of U.S. application Ser. No.15/886,611, filed on Feb. 1, 2018, the entire specification of which isincorporated herein by reference.

BACKGROUND Field

Aspects of the present disclosure relate generally to isolationstructures, and more particularly, to gate tie-off structures.

Background

A semiconductor chip (die) may include a large number of transistors,and isolation structures for providing electrical isolation betweentransistors on the chip. An example of such an isolation structure is agate tie-off structure, in which a dummy gate is electrically coupled(tied) to a source.

SUMMARY

The following presents a simplified summary of one or more embodimentsin order to provide a basic understanding of such embodiments. Thissummary is not an extensive overview of all contemplated embodiments,and is intended to neither identify key or critical elements of allembodiments nor delineate the scope of any or all embodiments. Its solepurpose is to present some concepts of one or more embodiments in asimplified form as a prelude to the more detailed description that ispresented later.

A first aspect relates to a chip. The chip includes a first gate, afirst source, a first source contact disposed on the first source, afirst metal interconnect above the first source contact and the firstgate, a first gate contact electrically coupling the first gate to thefirst metal interconnect, and a first via electrically coupling thefirst source contact to the first metal interconnect. The chip alsoincludes a second gate, a second source, a second source contactdisposed on the second source, a second metal interconnect above thesecond source contact and the second gate, a second gate contactelectrically coupling the second gate to the second metal interconnect,and a second via electrically coupling the second source contact to thesecond metal interconnect. Each of the first metal interconnect and thesecond metal interconnect extends along a first lateral direction, thefirst metal interconnect is aligned with the second metal interconnectin a second lateral direction, and the first lateral direction isapproximately perpendicular to the second lateral direction.

A second aspect relates to a chip. The chip includes a first gateextended along a second lateral direction, a first source electricallycoupled to a power rail, and a first metal interconnect extended along afirst lateral direction approximately perpendicular to the secondlateral direction, wherein the first metal interconnect lies above thefirst gate and the first source, and the first metal interconnect isconfigured to electrically couple the first gate to the first source.The chip also includes a second gate extended along the second lateraldirection, a second source electrically coupled to the power rail, and asecond metal interconnect extended along the first lateral direction,wherein the second metal interconnect lies above the second gate andsecond source, the second metal interconnect is configured toelectrically couple the second gate to the second source, and the firstmetal interconnect is aligned with the second metal interconnect in thesecond lateral direction.

To the accomplishment of the foregoing and related ends, the one or moreembodiments include the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative aspects ofthe one or more embodiments. These aspects are indicative, however, ofbut a few of the various ways in which the principles of variousembodiments may be employed and the described embodiments are intendedto include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a gate tie-off structure according to certainaspects of the present disclosure.

FIG. 2A shows an example of source-to-source abutment of two cellsaccording to certain aspects of the present disclosure.

FIG. 2B shows an example of source-to-drain abutment of two cellsaccording to certain aspects of the present disclosure.

FIG. 2C shows an example of drain-to-drain abutment of two cellsaccording to certain aspects of the present disclosure.

FIG. 3A shows a top view of an exemplary gate tie-off structureincluding a metal interconnect according to certain aspects of thepresent disclosure.

FIG. 3B shows a side view of the exemplary gate tie-off structure shownin FIG. 3A.

FIG. 4A shows a top view of an example of drain-to-drain abutment of afirst cell and a second cell according to certain aspects of the presentdisclosure.

FIG. 4B shows a side view of the drain-to-drain abutment shown in FIG.4A.

FIG. 5A shows a top view of an example of source-to-drain abutment of afirst cell and a second cell according to certain aspects of the presentdisclosure.

FIG. 5B shows a side view of the source-to-drain abutment shown in FIG.5A.

FIG. 6A shows a top view of an example of source-to-source abutment of afirst cell and a second cell according to certain aspects of the presentdisclosure.

FIG. 6B shows a side view of the source-to-source abutment shown in FIG.6A.

FIG. 7A shows a top view of another example of drain-to-drain abutmentof a first cell and a second cell according to certain aspects of thepresent disclosure.

FIG. 7B shows a side view of the drain-to-drain abutment shown in FIG.7A.

FIG. 8A shows a top view of another example of source-to-drain abutmentof a first cell and a second cell according to certain aspects of thepresent disclosure.

FIG. 8B shows a side view of the source-to-drain abutment shown in FIG.8A.

FIG. 9A shows a top view of another example of source-to-source abutmentof a first cell and a second cell according to certain aspects of thepresent disclosure.

FIG. 9B shows a side view of the source-to-source abutment shown in FIG.9A.

FIG. 10A shows a top view of an example of a cell including a gatetie-off structure according to certain aspects of the presentdisclosure.

FIG. 10B shows a side view of the cell shown in FIG. 10A.

FIG. 11 show a perspective view of an example in which the cell in FIG.10A includes multiple fins according to certain aspects of the presentdisclosure.

FIG. 12A shows a top view of another example of a cell including a gatetie-off structure according to certain aspects of the presentdisclosure.

FIG. 12B shows a side view of the cell shown in FIG. 12A.

FIG. 13A shows an example of multiple tracks for a cell according tocertain aspects of the present disclosure.

FIG. 13B shows an example of multiple tracks for multiple cellsaccording to certain aspects of the present disclosure.

DETAILED DESCRIPTION

The detailed description set forth below, in connection with theappended drawings, is intended as a description of variousconfigurations and is not intended to represent the only configurationsin which the concepts described herein may be practiced. The detaileddescription includes specific details for the purpose of providing athorough understanding of the various concepts. However, it will beapparent to those skilled in the art that these concepts may bepracticed without these specific details. In some instances, well-knownstructures and components are shown in block diagram form in order toavoid obscuring such concepts.

A semiconductor chip (die) may include a large number of transistors,and isolation structures for providing electrical isolation betweentransistors on the chip. An example of such an isolation structure is agate tie-off structure, in which a dummy gate is electrically coupled(tied) to a source. Coupling the dummy gate to the source turns off thechannel under the dummy gate, thereby providing electrical isolationbetween transistors on opposite sides of the dummy gate.

FIG. 1 shows a top view of an example of a cell 105 including a gatetie-off structure according to certain aspects of the presentdisclosure. In this example, the cell 105 includes an active region 110,and multiple gates 120, 122, 124, 126, 128 and 130. For a fin-type fieldeffect transistor (finFET) process, the active region 110 may includemultiple fins that extend across the cell 105 in lateral direction 150.For ease of illustration, the individual fins are not shown in FIG. 1.As used herein, the term “lateral” refers to a direction that runsparallel with the substrate of the chip.

The active region 110 and gates 122, 126 and 128 form transistors in thecell 105. For the example of a finFET process, each gate 122, 126 and128 is formed over a respective portion of the fins of the active region110 with a thin dielectric layer disposed between the gate and the fins.In this example, each gate 122, 126 and 128 forms the gate of atransistor in the cell 110 with portions of the fins on opposite sidesof the gate forming the source and drain of the transistor.

In the example shown in FIG. 1, the gate tie-off structure includes gate124 and a contact 135 electrically coupling (tying) gate 124 to aneighboring (adjacent) source 140. The contact 135 may be coupled to thesource through a source contact (not shown in FIG. 1) disposed on thesource 140. Coupling gate 124 to the source 140 turns off the channelunder gate 124, thereby providing electrical isolation betweentransistors on opposite sides of gate 124. The contact 135 is formedfrom a contact layer, which may also be used to form gate contacts (notshown) for coupling the gates of the transistors to upper interconnectmetal layers (not shown). If the source 140 is the source of a p-typefield effect transistor (PFET), then the source 140 may be coupled to avoltage supply rail, and, if the source 140 is the source of an n-typefield effect transistor (NFET), then the source 140 may be coupled to aground rail.

The gate tie-off structure shown in FIG. 1 provides electrical isolationbetween transistors on opposite sides of gate 124 without having to cut(break) the fins under gate 124. This is because the gate-off structureturns off the channel under gate 124 by coupling (tying) gate 124 to thesource 140. As a result, the fins of the active region 110 may runcontinuously under gate 124.

In an alternative electrical isolation approach, the fins are cut undergate 124 to provide electrical isolation between transistors on oppositesides of gate 124. In this approach, the space formed by cutting thefins is filled with an electrical isolation material (e.g., dielectricmaterial), which introduces stresses in the fins that is sensitive toprocess variation. The stresses in the fins change the electricalcharacteristics of the transistors in the cell 105. Since the stressesin the fins are sensitive to process variation, the resulting changes inthe electrical characteristics of the transistors are also sensitive toprocess variation, leading to uncertainty in the electricalcharacteristics of the transistors. The gate tie-off structure overcomesthis drawback by providing electrical isolation between transistors onopposite sides of gate 124 without having to cut (break) the fins undergate 124.

The exemplary gate tie-off structure shown in FIG. 1 may be used toelectrically isolate transistors in two cells that abut each other. Inthis regard, FIGS. 2A-2C below show examples of three different abutmentscenarios for two cells.

FIG. 2A shows a top view of an example of source-to-source abutment of afirst cell 205 and a second cell 208. The first cell 205 includesmultiple gates 210, 212 and 214, a source (labeled “S”), and a drain(labeled “D”). Gate 212, the source, and the drain form a transistor inthe first cell 205. The first cell 205 also includes a drain contact 216disposed on the drain, and a source contact 218 disposed on the source.The drain and source contacts 216 and 218 may be formed from a contactlayer, which may be different from the contact layer used to form gatecontacts (not shown). The first cell 205 also includes a via 222electrically coupling the source contact 218 (and hence the source) to apower rail 224, which lies above the source contact 218. For the examplein which the source is the source of a PFET, the power rail 224 may be avoltage supply rail, and, for the example in which the source is thesource of an NFET, the power rail may be a ground rail. Note thatstructures below the power rail 224 are shown in dashed lines in FIG.2A.

The first cell 205 further includes a gate tie-off structure includinggate 214 and a contact 220 electrically coupling (tying) gate 214 to thesource contact 218 (and hence the source in the first cell 205). Bycoupling gate 214 to the source, the gate tie-off structure turns offthe channel under gate 214, thereby providing electrical isolation forthe transistor in the first cell 205.

The second cell 208 includes multiple gates 226, 228 and 230, a source(labeled “S”), and a drain (labeled “D”). Gate 228, the source, and thedrain form a transistor in the second cell 208. The second cell 208 alsoincludes a drain contact 232 disposed on the drain, and a source contact234 disposed on the source. The drain and source contacts 232 and 234may be formed from the same contact layer used to form the drain andsource contacts 216 and 218 in the first cell 205. The second cell 208also includes a via 238 electrically coupling the source contact 234(and hence the source) to a power rail 240, which lies above the sourcecontact 234. Note that structures below the power rail 240 are shown indashed lines in FIG. 2A.

The second cell 208 further includes a gate tie-off structure includinggate 226 and a contact 236 electrically coupling (tying) gate 226 to thesource contact 234 (and hence the source in the second cell 208). Bycoupling gate 226 to the source, the gate tie-off structure turns offthe channel under gate 226, thereby providing electrical isolation forthe transistor in the second cell 208.

The right-hand side of FIG. 2A shows an example in which the source sideof the first cell 205 abuts the source side of the second cell 208. Inthis example, gates 214 and 226 are merged into gate 242, in which gate242 is coupled to the source in the first cell 205 by contact 220 andcoupled to the source in the second cell 208 by contact 236. Also, thesources in the first and second cells are coupled to a common power rail244, which lies above the source contacts 218 and 238. Since gate 242 iscoupled (tied) to the sources in the first cell 205 and the second cell208, the channel under gate 242 is turned off, thereby providingelectrical isolation between the transistors in the first cell 205 andthe second cell 208. In this example, gate 242 is a dummy gate coupledto two neighboring sources by contacts 220 and 236. Thus, the gatetie-off structure shown in FIG. 1 supports source-to-source abutment oftwo cells.

FIG. 2B shows a top view of an example of source-to-drain abutment of afirst cell 246 and a second cell 248. The first cell 246 is structurallythe same as the first cell 205 discussed above with reference to FIG.2A. Accordingly, the description of the first cell 205 provided aboveapplies to the first cell 246 in FIG. 2B.

The second cell 248 includes multiple gates 250, 252 and 254, a source(labeled “S”), and a drain (labeled “D”). Gate 252, the source, and thedrain form a transistor in the second cell 248. The second cell 248 alsoincludes a drain contact 256 disposed on the drain, and a source contact258 disposed on the source. The second cell 248 also includes a via 262electrically coupling the source contact 258 (and hence the source) to apower rail 266, which lies above the source contact 258. Note thatstructures below the power rail 266 are shown in dashed lines.

The second cell 248 further includes a gate tie-off structure includinggate 254 and a contact 260 electrically coupling (tying) gate 254 to thesource contact 258 (and hence the source in the second cell 248). Bycoupling gate 254 to the source, the gate tie-off structure turns offthe channel under gate 254, thereby providing electrical isolation forthe transistor in the second cell 248.

The right-hand side of FIG. 2B shows an example in which the source sideof the first cell 246 abuts the drain side of the second cell 248. Inthis example, gates 214 and 250 are merged into gate 268, in which gate268 is coupled to the source in the first cell 246 by contact 220. Also,the sources in the first and second cells are coupled to a common powerrail 270. Since gate 268 is coupled (tied) to the source in the firstcell 246, the channel under gate 268 is turned off, thereby providingelectrical isolation between the transistors in the first cell 246 andthe second cell 248. In this example, gate 268 is a dummy gate coupledto one of two neighboring sources by contact 220. Thus, the gate tie-offstructure shown in FIG. 1 supports source-to-drain abutment of twocells.

FIG. 2C shows a top view of an example of drain-to-drain abutment of afirst cell 272 and a second cell 274. As explained further below, thegate tie-off structure discussed above does not support drain-to-drainabutment of two cells.

The first cell 272 includes multiple gates 276, 278 and 280, a source(labeled “S”), and a drain (labeled “D”). Gate 278, the source, and thedrain form a transistor in the first cell 272. The first cell 272 alsoincludes a drain contact 282 disposed on the drain, and a source contact284 disposed on the source. The drain and source contacts 282 and 284may be formed from a contact layer, which may be different from thecontact layer used to form gate contacts (not shown). The first cell 272also includes a via 288 electrically coupling the source contact 284(and hence the source) to a power rail 290, which lies above the sourcecontact 284. Note that structures below the power rail 290 are shown indashed lines in FIG. 2C.

The first cell 272 further includes a gate tie-off structure includinggate 276 and a contact 286 electrically coupling (tying) gate 276 to thesource contact 284 (and hence the source in the first cell 272). Bycoupling gate 276 to the source, the gate tie-off structure turns offthe channel under gate 276, thereby providing electrical isolation forthe transistor in the first cell 272.

The second cell 274 is structurally the same as the second cell 248discussed above with reference to FIG. 2B. Accordingly, the descriptionof the second cell 248 provided above applies to the second cell 274 inFIG. 2C.

The right-hand side of FIG. 2C shows an example in which the drain sideof the first cell 272 abuts the drain side of the second cell 274. Gates280 and 250 are merged into gate 292, and the sources in the first andsecond cells are coupled to a common power rail 294. In this example,gate 292 is surrounded by drains on both sides with no neighboringsource. Thus, gate 292 cannot be coupled (tied) to a source using acontact to provide electrical isolation between the transistors in firstcell 272 and the second cell 274. Therefore, the gate tie-off structurediscussed above does not support drain-to-drain abutment of two cells.

Another challenge with the gate tie-off structure discussed above isthat it may be difficult to control alignment of the contact couplingthe dummy gate to a source. Misalignment of the contact may cause thecontact to touch the gate of an adjacent transistor, shorting the gateof the transistor to the source. This may permanently turn off thetransistor, thereby rendering the transistor non-functional.

Accordingly, there is a need for gate tie-off structures that overcomeone or more of the drawbacks discussed above.

In this regard, FIG. 3A shows a top view of an exemplary gate tie-offstructure for a cell 310 on a chip according to certain aspects of thepresent disclosure. As discussed further before, the exemplary gatetie-off structure shown in FIG. 3A supports drain-to-drain abutment oftwo cells.

In this example, the cell 310 includes multiple gates 312, 314 and 316,a source (labeled “S”), and a drain (labeled “D”). Gates 312 and 316 arelocated on the boundary of the cell 310 in this example. Gate 314, thesource, and the drain form a transistor in the cell 310. The cell 310also includes a drain contact 318 disposed on the drain, and a sourcecontact 320 disposed on the source. The drain and source contacts 318and 320 may be formed from a contact layer, which may be different fromthe contact layer used to form gate contacts. The cell 310 also includesa via 330 electrically coupling the source contact 320 (and hence thesource) to a power rail 335, which lies above the source contact 320.Note that structures below the power rail 335 are shown in dashed linesin FIG. 3A. For the example in which the transistor in the cell 310 is aPFET, the power rail 335 may be a voltage supply rail (e.g., Vdd rail),and, for the example in which the transistor in the cell 310 is an NFET,the power rail 335 may be a ground rail (e.g., Vss rail).

The gate tie-off structure includes a metal interconnect 322, which maybe formed from a metal layer (i.e., bottom-most metal layer) in the backend of line (BEOL) of the chip (die). The metal interconnect 322 liesabove the gates 312, 314 and 316, the drain contact 318, and the sourcecontact 320. Note that structures under the metal interconnect 322 areshown in dashed lines. In the example in FIG. 3A, the metal interconnect322 extends across the cell 310 in lateral direction 340. In someaspects, the metal interconnect 322 may be formed from the same metallayer used to form the power rail 335 (e.g., using lithographic andetching processes), and may run parallel to the power rail 335. Forexample, the metal interconnect 322 and the power rail 335 may be formedfrom the same metal layer (e.g., bottom-most metal layer) in the BEOL ofthe chip.

The gate tie-off structure also includes a first gate contact 324disposed between gate 312 and the metal interconnect 322, a second gatecontact 326 disposed between gate 316 and the metal interconnect 322,and a via 328 disposed between the source contact 320 and the metalinterconnect 322. In this example, the first gate contact 324 couplesgate 312 to the metal interconnect 322, the second gate contact 326couples gate 316 to the metal interconnect 322, and the via 328 couplesthe source contact 320 to the metal interconnect 322. Thus, gate 312 iselectrically coupled to the source contact 320 (and hence the source)through the first gate contact 324, the metal interconnect 322, and thevia 328. Similarly, gate 316 is electrically coupled to the sourcecontact 320 (and hence the source) through the second gate contact 326,the metal interconnect 322, and the via 328. Thus, in this example,gates 312 and 316 are dummy gates that are electrically coupled (tied)to the source through the metal interconnect 322. Since gates 312 and316 are located on the boundary of the cell 310, electrically couplinggates 312 and 316 to the source through metal interconnect 322 provideselectrical isolation for the transistor in the cell 310 from other cells(not shown).

FIG. 3B shows a side view of the exemplary gate tie-off structure. Asshown in FIG. 3B, the metal interconnect 322 passes (crosses) over thedrain contact 318, and is separated from the drain contact 318 in thevertical direction 344 by a space (gap). The space may be filled with anelectrical isolation material to electrically isolate the metalinterconnect 322 from the drain contact 318, allowing the metalinterconnect 322 to pass over the drain contact 318 without electricallyshorting to the drain contact 318. The metal interconnect 322 alsopasses (crosses) over the gate 314 of the transistor in the cell 310,and is separated from the gate 314 of the transistor in the verticaldirection 344 by a space (gap). The space may be filled with anelectrical isolation material to electrically isolate the metalinterconnect 322 from the gate 314, allowing the metal interconnect 322to pass over the gate 314 without electrically shorting to the gate 314.As used herein, the term “vertical” refers to a direction that runsperpendicular to the substrate of the chip.

Thus, the metal interconnect 322 passes (crosses) over the drain contact318 and the gate 314 of the transistor without electrically shorting tothe drain contact 318 and the gate 314 of the transistor. This allowsthe metal interconnect to couple dummy gate 316 to the source contact320 (and hence the source) even though dummy gate 316 is not adjacent tothe source. In contrast, the gate tie-off structure discussed above withreference to FIG. 1 requires that a dummy gate have a neighboring(adjacent) source in order to couple (tie) the dummy gate to a source.The exemplary gate tie-off structure shown in FIGS. 3A and 3B does nothave this restriction, allowing for drain-to-drain abutment, asdiscussed further below.

In the example shown in FIG. 3B, the source and the drain are depictedas doped regions in the substrate of the chip (die) for a planartransistor. However, it is to be appreciated that for the example of afinFET, the source and drain may be formed from multiple fins (not shownin FIG. 3B) that extend across the cell 310 in lateral direction 340.Accordingly, it is to be appreciated that aspects of the presentdisclosure apply to both planar transistors and finFETs.

As shown in FIG. 3A, the drain contact 318 extends under the metalinterconnect 322 in lateral direction 342. This allows the drain contact318 to extend over a larger area of the drain, which reduces the contactresistance of the drain. The drain contact 318 is able to extend underthe metal interconnect 322 because the metal interconnect 322 isseparated from the drain contact 310 in the vertical direction 344 by aspace (gap) that prevents shorting of the metal interconnect 322 to thedrain contact 318. For a finFET process, this allows the drain contact318 to extend across the cell 310 in lateral direction 342, and makecontact with all of the fins for low contact resistance.

Without the space (gap) between the metal interconnect 322 and the draincontact 318, the drain contact 318 is not able to pass under the metalinterconnect 322 without shorting the drain contact 318 to the metalinterconnect 322. In this case, the drain contact can only partiallyextend over the drain, in which the drain contact and the metalinterconnect need to be separated by a margin in lateral direction 342to prevent the drain contact from shorting to the metal interconnect.The partial drain contact in this case may significantly increase thecontact resistance of the drain compared with the drain contact 318shown in FIG. 3A, which may extend fully across the drain in lateraldirection 342 for low contact resistance.

In certain aspects, gate contacts 324 and 326 are self-aligned gatecontacts that are formed using a self-aligned contact process. For eachgate, the self-aligned contact process may include the following steps.Spacers (e.g., nitrite spacers) may be formed on opposite sides of thegate, in which the space between the spacers is filled with a fillermaterial (e.g., oxide material). The filler material may then be removedusing a selective etching process that etches away the filler materialwithout etching away the spacers, thereby creating an opening betweenthe spacers. The resulting opening is directly above the gate and iselectrically isolated from neighboring drain/source contact(s) by thespacers. A metal may then be deposited in the opening to form therespective gate contact. The resulting gate contact is self-aligned.This is because the spacers (e.g., nitride spacers) define the openingin which the gate contact is formed, making formation of the gatecontact significantly more tolerant of gate contact patterningmisalignment. The self-aligned gate contact helps prevent misalignmentof the gate contact, which facilitates side-by-side placement of thegate contact and a neighboring drain/source contact without shorting thegate contact to the neighboring drain/source contact.

FIG. 3B shows an example in which the gate contacts 324 and 326 arecoupled directly to the metal interconnect 322. However, it is to beappreciated that the present disclosure is not limited to this example.For example, each of the gate contacts 324 and 326 may be coupled to themetal interconnect 322 through a respective via disposed between thegate contact and the metal interconnect 322.

Referring to FIG. 3A, it is to be appreciated that the drain contact 318may be coupled to a signal routing structure (not shown) for routingsignals to and/or from the drain. The routing structure may include avia (not shown) disposed on the drain contact 318, in which the via isoffset from the metal interconnect 322 in lateral direction 342 toprevent shorting of the drain to the metal interconnect 322. Similarly,is to be appreciated that the gate 314 of the transistor may be coupledto a signal routing structure (not shown) for routing signals to and/orfrom the gate 314. The routing structure may include a gate contact (notshown) disposed on the gate 314, in which the gate contact is offsetfrom the metal interconnect 322 in lateral direction 342 to preventshorting of the gate 314 to the metal interconnect 322.

It is to be appreciated that the cell 310 may include additionaltransistors between gates 312 and 316, in which gates 312 and 316 arecoupled to the source of at least one of the transistors in the cell 310through the metal interconnect 322. Since gates 312 and 316 are locatedon the boundary of the cell 310, coupling gates 312 and 316 to thesource of at least one of the transistors through the metal interconnect322 electrically isolates the transistors in the cell 310 from othercells (not shown). In this example, the metal interconnect 322 mayextend over the transistors in the cell 310 in lateral direction 340.

As discussed above, the exemplary gate tie-off structure shown in FIGS.3A and 3B supports drain-to-drain abutment of two cells. An example ofthis will now be discussed below with reference to FIGS. 4A and 4B.

FIG. 4A shows a top view of an example of drain-to-drain abutment of afirst cell 410 and a second cell 412. The first cell 410 is structurallythe same as the cell 310 discussed above with reference to FIGS. 3A and3B. Accordingly, the description of the cell 310 provided above appliesto the first cell 410.

The second cell 412 includes multiple gates 414, 416 and 418, a source(labeled “S”), and a drain (labeled “D”). Gates 414 and 418 are locatedon the boundary of the second cell 412 in this example. Gate 416, thesource, and the drain form a transistor in the second cell 412. Thesecond cell 412 also includes a drain contact 420 disposed on the drain,and a source contact 422 disposed on the source. The second cell 412also includes a via 432 electrically coupling the source contact 422(and hence the source) to a power rail 435, which lies above the sourcecontact 422. Note that structures below the power rail 435 are shown indashed lines.

The second cell 412 further includes a gate tie-off structure includinga metal interconnect 424, which may be formed from the same metal layeras the metal interconnect 322 of the first cell 410. The metalinterconnect 424 lies above the gates 414, 416 and 418, the draincontact 420, and the source contact 422. Note that structures under themetal interconnect 424 are shown in dashed lines. In the example shownin FIG. 4A, the metal interconnect 424 extends across the second cell412 in lateral direction 460.

The gate tie-off structure also includes a first gate contact 428coupling gate 414 to the metal interconnect 424, a second gate contact426 coupling gate 418 to the metal interconnect 424, and a via 430coupling the source contact 422 to the metal interconnect 424. In thisexample, gates 414 and 418 are dummy gates that are electrically coupled(tied) to the source through the metal interconnect 424.

FIG. 4B shows a side view of the gate tie-off structure of the secondcell 412. As shown in FIG. 4B, the metal interconnect 424 passes overthe drain contact 420 and is separated from the drain contact 420 in thevertical direction 470 by a space. This allows the drain contact 420 toextend under the metal interconnect 424 in lateral direction 465 toreduce the drain contact resistance. The metal interconnect 424 alsopasses over the gate 416 of the transistor in the second cell 412, andis separated from the gate 416 of the transistor in the verticaldirection 470 by a space.

The right-hand sides of FIGS. 4A and 4B show an example in which thedrain side of the first cell 410 abuts the drain side of the second cell412. Gates 316 and 414 are merged into gate 440, and the metalinterconnects 322 and 424 are combined into a common metal interconnect445, which extends across the first and second cells 410 and 412 inlateral direction 460. In this example, gate 440 is coupled to the metalinterconnect 445 through gate contact 442, which is disposed betweengate 440 and the metal interconnect 445. In addition, the sources in thefirst and second cells are coupled to a common power rail 450.

In this example, gate 440 at the drain-to-drain abutment is coupled(tied) to the sources in the first and second cells 410 and 412 throughthe metal interconnect 445. The metal interconnect 445 couples gate 440to the sources even though gate 440 does not have a neighboring source(i.e., gate 440 is surrounded by drains on both sides). This is becausethe interconnect 445 is able to cross over gates 314 and 416 to couplegate 440 to the source contacts 320 and 422, respectively. Since gate440 is coupled (tied) to the sources of the first and second cellsthrough the metal interconnect 445, the channel under gate 440 is turnedoff, thereby providing electrical isolation between the transistors inthe first and second cells. Therefore, the exemplary gate tie-offstructure according to aspects of the present disclosure supportsdrain-to-drain abutment of two cells. The exemplary gate tie-offstructure also supports source-to-drain abutment and source-to-sourceabutment as discussed further below.

In the example shown in FIG. 4A, the source contacts 320 and 422 arecoupled to the common power rail 450 through vias 330 and 432,respectively. For the example in which the transistors in the first andsecond cells are PFETs, the power rail 450 may be a voltage supply rail(e.g., Vdd rail), and, for the example in which the transistors in thefirst and second cells are NFETs, the power rail 450 may be a groundrail (e.g., Vss rail). In certain aspects, the power rail 450 may beformed (e.g., using lithographic and etching processes) from the samemetal layer (e.g., bottom-most metal layer of BEOL) as the metalinterconnect 445, and run parallel with the metal interconnect 445.

FIG. 5A shows a top view of an example of source-to-drain abutment of afirst cell 510 and a second cell 512. The first cell 510 includesmultiple gates 514, 516 and 518, a source (labeled “S”), and a drain(labeled “D”). Gates 514 and 518 are located on the boundary of thefirst cell 510 in this example. Gate 516, the source, and the drain forma transistor in the first cell 510. The first cell 510 also includes adrain contact 520 disposed on the drain, and a source contact 522disposed on the source. The first cell 510 also includes a via 532electrically coupling the source contact 522 (and hence the source) to apower rail 535, which lies above the source contact 522. Note thatstructures below the power rail 535 are shown in dashed lines.

The first cell 510 further includes a gate tie-off structure including ametal interconnect 524, which may be formed from a metal layer (e.g.,bottom-most metal layer) in the BEOL of the chip. The metal interconnect524 lies above the gates 514, 516 and 518, the drain contact 520, andthe source contact 522. Note that structures under the metalinterconnect 524 are shown in dashed lines. In the example shown in FIG.5A, the metal interconnect 524 extends across the first cell 510 inlateral direction 560.

The gate tie-off structure also includes a first gate contact 528coupling gate 514 to the metal interconnect 524, a second gate contact526 coupling gate 518 to the metal interconnect 524, and a via 530coupling the source contact 522 to the metal interconnect 524. In thisexample, gates 514 and 518 are dummy gates that are electrically coupled(tied) to the source through the metal interconnect 524.

FIG. 5B shows a side view of the gate tie-off structure of the firstcell 510. As shown in FIG. 5B, the metal interconnect 524 passes overthe drain contact 520 and is separated from the drain contact 520 in thevertical direction 570 by a space. This allows the drain contact 520 toextend under the metal interconnect 524 in lateral direction 565 toreduce the drain contact resistance. The metal interconnect 524 alsopasses over the gate 516 of the transistor in the first cell 510, and isseparated from the gate 516 of the transistor in the vertical direction570 by a space.

The second cell 512 is structurally the same as the second cell 412discussed above with reference to FIGS. 4A and 4B. Accordingly, thedescription of the second cell 412 provided above applies to the secondcell 512 shown in FIGS. 5A and 5B.

The right-hand sides of FIGS. 5A and 5B show an example in which thesource side of the first cell 510 abuts the drain side of the secondcell 512. Gates 518 and 414 are merged into gate 540, and the metalinterconnects 424 and 524 are combined into a common metal interconnect545, which extends across the first and second cells 510 and 512 inlateral direction 560. In this example, gate 540 is coupled to the metalinterconnect 545 through gate contact 542, which is disposed betweengate 540 and the metal interconnect 545. In addition, the sources in thefirst and second cells are coupled to a common power rail 550.

In this example, gate 540 at the source-to-drain abutment is coupled(tied) to the sources in the first and second cells 510 and 512 throughthe metal interconnect 545. Since gate 540 is coupled (tied) to thesources of the first and second cells through the metal interconnect545, the channel under gate 540 is turned off, thereby providingelectrical isolation between the transistors in the first and secondcells. Therefore, the exemplary gate tie-off structure according toaspects of the present disclosure supports source-to-drain abutment oftwo cells.

In the example shown in FIG. 5A, the source contacts 522 and 422 arecoupled to the common power rail 550 through vias 532 and 432,respectively. For the example in which the transistors in the first andsecond cells are PFETs, the power rail 550 may be a voltage supply rail(e.g., Vdd rail), and, for the example in which the transistors in thefirst and second cells are NFETs, the power rail 550 may be a groundrail (e.g., Vss rail). In certain aspects, the power rail 550 may beformed (e.g., using lithographic and etching processes) from the samemetal layer (e.g., bottom-most metal layer of BEOL) as the metalinterconnect 545, and run parallel with the metal interconnect 545.

FIG. 6A shows a top view of an example of source-to-source abutment of afirst cell 610 and a second cell 612. The first cell 610 is structurallythe same as the first cell 510 discussed above with reference to FIGS.5A and 5B. Accordingly, the description of the first cell 510 providedabove applies to the first cell 610 shown in FIGS. 6A and 6B.

The second cell 612 includes multiple gates 614, 616 and 618, a source(labeled “S”), and a drain (labeled “D”). Gates 614 and 618 are locatedon the boundary of the second cell 612 in this example. Gate 616, thesource, and the drain form a transistor in the second cell 612. Thesecond cell 612 also includes a drain contact 620 disposed on the drain,and a source contact 622 disposed on the source. The second cell 612also includes a via 632 electrically coupling the source contact 622(and hence the source) to a power rail 635, which lies above the sourcecontact 622. Note that structures below the power rail 635 are shown indashed lines.

The second cell 612 further includes a gate tie-off structure includinga metal interconnect 624, which may be formed from the same metal layeras the metal interconnect 524 of the first cell 610. The metalinterconnect 624 lies above the gates 614, 616 and 618, the draincontact 620, and the source contact 622. Note that structures under themetal interconnect 624 are shown in dashed lines. In the example shownin FIG. 6A, the metal interconnect 624 extends across the second cell612 in lateral direction 660.

The gate tie-off structure also includes a first gate contact 626coupling gate 614 to the metal interconnect 624, a second gate contact628 coupling gate 618 to the metal interconnect 624, and a via 630coupling the source contact 622 to the metal interconnect 624. In thisexample, gates 614 and 618 are dummy gates that are electrically coupled(tied) to the source through the metal interconnect 624.

FIG. 6B shows a side view of the gate tie-off structure of the secondcell 612. As shown in FIG. 6B, the metal interconnect 624 passes overthe drain contact 620 and is separated from the drain contact 620 in thevertical direction 670 by a space. The metal interconnect 624 alsopasses over the gate 616 of the transistor in the second cell 612, andis separated from the gate 616 of the transistor in the verticaldirection 670 by a space.

The right-hand sides of FIGS. 6A and 6B show an example in which thesource side of the first cell 610 abuts the source side of the secondcell 612. Gates 518 and 614 are merged into gate 640, and the metalinterconnects 524 and 624 are combined into a common metal interconnect645, which extends across the first and second cells 610 and 612 inlateral direction 660. In this example, gate 640 is coupled to the metalinterconnect 645 through gate contact 642, which is disposed betweengate 640 and the metal interconnect 645. In addition, the sources in thefirst and second cells are coupled to a common power rail 650.

In this example, gate 640 at the source-to-source abutment is coupled(tied) to the sources in the first and second cells 610 and 612 throughthe metal interconnect 645. Since gate 640 is coupled (tied) to thesources of the first and second cells through the metal interconnect645, the channel under gate 640 is turned off, thereby providingelectrical isolation between the transistors in the first and secondcells. Therefore, the exemplary gate tie-off structure according toaspects of the present disclosure supports source-to-source abutment oftwo cells.

In the example shown in FIG. 6A, the source contacts 522 and 622 arecoupled to the common power rail 650 through vias 532 and 632,respectively. For the example in which the transistors in the first andsecond cells are PFETs, the power rail 650 may be a voltage supply rail(e.g., Vdd rail), and, for the example in which the transistors in thefirst and second cells are NFETs, the power rail 650 may be a groundrail (e.g., Vss rail). In certain aspects, the power rail 650 may beformed (e.g., using lithographic and etching processes) from the samemetal layer (e.g., bottom-most metal layer of BEOL) as the metalinterconnect 645, and run parallel with the metal interconnect 645.

FIGS. 7A and 7B show a top view and a side view, respectively, ofanother example of drain-to-drain abutment of a first cell 710 and asecond cell 712. The first cell 710 is similar to the first cell 410 inFIGS. 4A and 4B, in which elements that are common to both cells 710 and410 are identified by the same reference numbers. The first cell 710differs from the first cell 410 in FIGS. 4A and 4B in that the gatecontact 324 in FIGS. 4A and 4B is omitted. As a result, gate 312 is notcoupled to the metal interconnect 722 of the first cell 710. Also, theinterconnect 722 differs from the interconnect 322 in FIGS. 4A and 4B inthat the interconnect 722 does not extend over gate 312.

The second cell 712 is similar to the second cell 412 in FIGS. 4A and4B, in which elements that are common to both cells 712 and 412 areidentified by the same reference numbers. The second cell 712 differsfrom the second cell 412 in FIGS. 4A and 4B in that the gate contact 426in FIGS. 4A and 4B is omitted. As a result, gate 418 is not coupled tothe metal interconnect 724 of the second cell 712. Also, theinterconnect 724 differs from the interconnect 424 in FIGS. 4A and 4B inthat the interconnect 724 does not extend over gate 418.

The right-hand sides of FIGS. 7A and 7B show an example in which thedrain side of the first cell 710 abuts the drain side of the second cell712. Gates 316 and 414 are merged into gate 440, and the metalinterconnects 722 and 724 are combined into a common metal interconnect745. In this example, gate 440 is coupled to the metal interconnect 745through gate contact 442, which is disposed between gate 440 and themetal interconnect 745. As shown in FIGS. 7A and 7B, the gate 440 at thedrain-to-drain abutment is electrically coupled to the sources in thefirst and second cells 710 and 712 through the metal interconnect 745.This turns off the channel under gate 440, thereby providing electricalisolation between the transistors in the first and second cell 710 and712. The interconnect 745 couples gate 440 to the sources even thoughgate 440 is surrounded on both sides by drain contacts 318 and 420 bycrossing over the drain contacts 318 and 420 and gates 314 and 416, asshown in FIG. 7B.

FIGS. 8A and 8B show a top view and a side view, respectively, ofanother example of source-to-drain abutment of a first cell 810 and asecond cell 812. The first cell 810 is similar to the first cell 510 inFIGS. 5A and 5B, in which elements that are common to both cells 810 and510 are identified by the same reference numbers. The first cell 810differs from the first cell 510 in FIGS. 5A and 5B in that the gatecontact 526 in FIGS. 5A and 5B is omitted. As a result, gate 518 is notcoupled to the metal interconnect 824 of the first cell 810. Also, theinterconnect 824 differs from the interconnect 524 in FIGS. 5A and 5B inthat the interconnect 824 does not extend over gate 518.

The second cell 812 is similar to the second cell 512 in FIGS. 5A and5B, in which elements that are common to both cells 812 and 512 areidentified by the same reference numbers. The second cell 812 differsfrom the second cell 512 in FIGS. 5A and 5B in that the gate contact 426in FIGS. 5A and 5B is omitted. As a result, gate 418 is not coupled tothe metal interconnect 826 of the second cell 812. Also, theinterconnect 826 differs from the interconnect 424 in FIGS. 5A and 5B inthat the interconnect 826 does not extend over gate 418.

The right-hand sides of FIGS. 8A and 8B show an example in which thesource side of the first cell 810 abuts the drain side of the secondcell 812. Gates 518 and 414 are merged into gate 540, and the metalinterconnects 824 and 826 are combined into a common metal interconnect845. In this example, gate 540 is coupled to the metal interconnect 845through gate contact 542, which is disposed between gate 540 and themetal interconnect 845. As shown in FIGS. 8A and 8B, the gate 540 at thesource-to-drain abutment is electrically coupled to the sources in thefirst cell 810 and the second cell 812 through the metal interconnect845. This turns off the channel under gate 440, thereby providingelectrical isolation between the source in the first cell 810 and thedrain in the second cell 812.

FIGS. 9A and 9B show a top view and a side view, respectively, ofanother example of source-to-source abutment of a first cell 910 and asecond cell 912. The first cell 910 is similar to the first cell 610 inFIGS. 6A and 6B, in which elements that are common to both cells 910 and610 are identified by the same reference numbers. The first cell 910differs from the first cell 610 in FIGS. 6A and 6B in that the gatecontact 526 in FIGS. 6A and 6B is omitted. As a result, gate 518 is notcoupled to the metal interconnect 924 of the first cell 910. Also, theinterconnect 924 differs from the interconnect 524 in FIGS. 6A and 6B inthat the interconnect 924 does not extend over gate 518.

The second cell 912 is similar to the second cell 612 in FIGS. 6A and6B, in which elements that are common to both cells 912 and 612 areidentified by the same reference numbers. The second cell 912 differsfrom the second cell 612 in FIGS. 6A and 6B in that the gate contact 626in FIGS. 6A and 6B is omitted. As a result, gate 614 is not coupled tothe metal interconnect 926 of the second cell 912. Also, theinterconnect 926 differs from the interconnect 624 in FIGS. 6A and 6B inthat the interconnect 926 does not extend over gate 614.

The right-hand sides of FIGS. 9A and 9B show an example in which thesource side of the first cell 910 abuts the source side of the secondcell 912. Gates 518 and 614 are merged into gate 640 at thesource-to-source abutment of the first and second cells 910 and 912. Inthis example, gate 640 is floating (i.e., not coupled to metalinterconnect 924 or metal interconnect 926). Also, gate 640 issurrounded by the sources in the first and second cells 910 and 912, inwhich the sources are biased at the same potential by the common powerrail 650 (e.g., Vdd or Vss). Since the sources in the first and secondcells 910 and 912 are at the same potential in this example, gate 640does not need to provide electrical isolation between the sources, andtherefore does not need to be tied off in this example.

Gate tie-off structures according to aspects of the present disclosuremay be used within a cell to tie off one or more gates within the cell.In this regard, FIG. 10A shows a top view of an exemplary cell 1010including multiple gates 1012, 1014, 1016, 1018, 1020, 1022 and 1024,sources (labeled “S”), and drains (labeled “D”). In this example, eachsource is located between a respective pair of gates, and each drain islocated between a respective pair of gates. The cell 1010 also includesdrain contacts 1026, 1030, 1032 and 1036, in which each drain contact isdisposed on a respective one of the drains. The cell 1010 also includessource contacts 1028 and 1034, in which each source contact is disposedon a respective one of the sources. The cell further includes a powerrail 1060 and vias 1040 and 1042 coupling the source contacts 1028 and1034, respectively, to the power rail 1060.

The cell 1010 includes a gate tie-off structure including a metalinterconnect 1050, which may be formed from the same metal layer as thepower rail 1060 or a different metal layer. The metal interconnect 1050lies above gates 1016 and 1018, drain contact 1030 and source contact1028. Note that structures under the metal interconnect 1050 are shownin dashed lines. In the example in FIG. 10A, the metal interconnect 1050extends partially across the cell 1010 in lateral direction 1062.

The gate tie-off structure also includes a gate contact 1054 disposedbetween gate 1018 and the metal interconnect 1050, and a via 1052disposed between the source contact 1028 and the metal interconnect1050. In this example, the gate contact 1054 couples gate 1018 to themetal interconnect 1050, and the via 1052 couples the source contact1028 to the metal interconnect 1050. Thus, gate 1018 is electricallycoupled to the source contact 1028 (and hence the respective source)through the gate contact 1054, the metal interconnect 1050, and the via1052. Thus, in this example, gate 1018 is a dummy gate that iselectrically coupled (tied) to one of the sources of the cell 1010through the metal interconnect 1050 to provide electrical isolationbetween transistors on opposite sides of gate 1018.

FIG. 10B shows a side view of the exemplary gate tie-off structure. Asshown in FIG. 10B, the metal interconnect 1050 passes (crosses) overdrain contact 1030, and is separated from drain contact 1030 in thevertical direction 1066 by a space. Similarly, the metal interconnect1050 passes (crosses) over gate 1016, and is separated from gate 1016 inthe vertical direction 1066 by a space. This allows the metalinterconnect 1050 to cross over drain contact 1030 and gate 1016 tocouple gate 1018 to source contact 1028 without shorting the metalinterconnect 1050 to the drain contact 1030 and gate 1016. The verticalspace between the drain contact 1030 and the metal interconnect 1050allows the drain contact 1030 to extend under the metal interconnect1050 in lateral direction 1064, as shown in FIG. 10A.

In the example shown in FIG. 10B, the sources and the drains aredepicted as doped regions in the substrate of the chip (die) for aplanar transistor. However, it is to be appreciated that for the exampleof a finFET, the source and drain may be formed from multiple fins thatextend across the cell 1010 in lateral direction 1062. In this regard,FIG. 11 shows a perspective view of a portion of the cell 1010 in whichthe cell 1010 includes multiple fins 1110 that extend across the cell1010 in lateral direction 1062. In this example, each of gates 1016 and1018 is formed over a respective portion of the fins 1110 with a thindielectric layer (not shown) disposed between the gate and the fins1110. Thus, in this example, the fins run continuously through thegates. The drain contact 1030 is disposed on a portion of the fins 1110forming the respective drain, and the source contact 1028 is disposed ona portion of the fins 1110 forming the respective source.

As shown in FIG. 11, the vertical space (gap) between the metalinterconnect 1050 and the drain contact 1030 in vertical direction 1066allows the drain contact 1030 to extend under the metal interconnect1050 in lateral direction 1064. The extension of the drain contact 1030in lateral direction 1064 allows the drain contact 1030 to makeelectrical contact with all of the fins 1110 for low drain contactresistance. The space (gap) between the drain contact 1030 and the metalinterconnect 1050 may be filled with an electrical isolation material.

Although FIG. 11 shows an example in which the cell 1010 include threefins, it is to be appreciated that the cell 1010 may include a differentnumber of fins. Also, although FIG. 11 shows an example in which eachfin has a rectangular cross section, it is to be appreciated that eachfin may have another cross-sectional shape (e.g., a tampered shape).

It is to be appreciated that the fins 1110 may be used in any of theembodiments discussed above in which the fins may extend across one ormore cells. For the examples in which two cells abut each other, thefins may run continuously through the gate located at the abutment ofthe cells (e.g., gate 440, gate 540 or gate 640). In this case, the gateat the abutment may be tied off to provide electrical isolation betweenthe two cells without cutting (breaking) the fins under the gate.

It is to be appreciated that the cell 1010 may also include one or moreadditional gate tie-off structures (not shown) in addition to theexemplary gate tie-off structure shown in FIGS. 10A and 10B. In thiscase, the one or more additional gate tie-off structures and theexemplary gate tie-off structure shown in FIGS. 10A and 10B may share acommon metal interconnect that extends across the cell 1010 in lateraldirection 1062.

In this regard, FIG. 12A shows a top view of an exemplary cell 1210including a metal interconnect 1250 that extends across the cell 1210.The cell 1210 is similar to the cell 1010 in FIG. 10A, in which elementsthat are common to both cells 1010 and 1210 are identified by the samereference numbers.

The metal interconnect 1250 in FIG. 12A differs from the metalinterconnect 1050 shown in FIG. 10A in that metal interconnect 1250extends across the cell 1210. The metal interconnect 1250 may be formedfrom the same metal layer as the power rail 1060 or a different metallayer. The metal interconnect 1250 lies above the gates 1012, 1014,1016, 1018, 1020, 1022 and 1024, the drain contacts 1026, 1030, 1032 and1036, and the source contacts 1028 and 1034. Note that structures underthe metal interconnect 1250 are shown in dashed lines.

As shown in FIG. 12A, gate contact 1054 couples gate 1018 to the metalinterconnect 1250, and via 1052 couples the source contact 1028 to themetal interconnect 1250, similar to the cell 1010 in FIG. 10A. The cell1250 also includes gate contact 1252 disposed between gate 1012 and themetal interconnect 1250, and gate contact 1254 coupled between gate 1024and the metal interconnect 1250. Gate contact 1252 couples gate 1012 tothe metal interconnect 1250, and gate contact 1254 couples gate 1024 tothe metal interconnect 1250. Thus, gate 1012 is coupled to the sourcecontact 1028 (and hence the respective source) through the metalinterconnect 1250, and gate 1024 is coupled to the source contact 1028(and hence the respective source) through the metal interconnect 1250.Since gates 1012 and 1024 are located on the boundary of the cell 1250,electrically coupling gates 1012 and 1024 to the source through metalinterconnect 1250 provides electrical isolation for the transistors inthe cell 1210 from other cells (not shown).

FIG. 12B shows a side view of the cell 1210. As shown in FIG. 12B, themetal interconnect 1250 passes (crosses) over the drain contacts 1026,1030, 1032 and 1036, and is separated from the drain contacts in thevertical direction 1066 by a space. This allows the metal interconnect1250 to cross over the drain contacts without shorting the metalinterconnect 1250 to the drain contacts. Also, in this example, themetal interconnect 1250 passes (crosses) over gates 1014, 1016, 1020 and1022 and is separated from these gates in the vertical direction 1066 bya space. This allows the metal interconnect 1250 to cross over thesegates without shorting the metal interconnect 1250 to these gates.

In the example shown in FIGS. 12A and 12B, the cell 1210 also includes avia 1256 coupling source contact 1034 to the metal interconnect 1250.Thus, in this example, gate 1018 is coupled to two sources through themetal interconnect 1250, in which gate 1018 is located between the twosources.

In the example shown in FIG. 12A, the cell 1210 includes a continuousactive region 1260 (represented as a shaded region in FIG. 12A) thatextends across the cell 1210 in lateral direction 1062. In this example,at least a portion of each of the gates 1014, 1016, 1018, 1020 and 1022,each of the sources, and each of the drains is within the continuousactive region 1260. For a FinFET process, the continuous active region1260 includes fins that extend across the cell 1210 in lateral direction1062. In this example, the fins run continuously through the gates 1014,1016, 1018, 1020 and 1022 without cuts (breaks) in the fins.

The exemplary cells discussed above may be predefined in a standard celllibrary that defines various cells that can be placed on a chip (die)for a certain semiconductor processor. For each cell in the celllibrary, the cell library may define a layout of transistors in thecell, an interconnect structure for interconnecting transistors in thecell, and/or a gate tie-off structure for the cell. Multiple instancesof a cell in the cell library may be placed on the chip (die).

In certain aspects, each cell in the cell library may be configured toperform a respective logic function. In these aspects, the function of acircuit may be broken down into multiple logic functions during thedesign phase, where each logic function may be performed by one of thecells in the cell library. The cells that perform the logic functionsmay then be paced on the chip and interconnected to implement thecircuit on the chip. The cells may be interconnected by upper metallayers in the BEOL. Thus, in this example, the cells serve as buildingblocks for the circuit.

Layout parameters for cells on a chip may include tracks, which defineavailable paths in the cells for metal lines formed from a particularmetal layer (e.g., the bottom-most metal layer of the BEOL). In thisregard, FIG. 13A illustrates multiple tracks for an exemplary cell 1310according to certain aspects of the present disclosure. In FIG. 13A, thetracks are labeled T0 to T7 and are represented by multiple linesextending across the cell 1310 in lateral direction 1330. The tracks runparallel with one another and are spaced apart in lateral direction1340, where lateral direction 1340 is approximately perpendicular tolateral direction 1330. As used herein, the term “approximatelyperpendicular” indicates that the angle between two directions isbetween 85 and 95 degrees. It is to be appreciated that the cell 1310 isnot limited to the exemplary number of tracks shown in FIG. 13A, andthat the cell 1310 may have a different number of tracks.

The tracks define available paths in the cell 1310 for metal linesformed from a particular metal layer (e.g., the bottom-most metal layerof the BEOL). In other words, the tracks define where metal lines formedfrom the metal layer can be placed on the cell. In this example, a metalinterconnect may be placed on one of the tracks to tie off one or moregates in the cell 1310, and a power rail may be placed on a differentone of the tracks. In addition, metal lines used for signal routing maybe placed on one or more tracks that are different from the tracks usedfor the metal interconnect and the power rail. For example, these metallines may be used for routing signals to or from drain(s) in the cell,and/or routing signals to or from gate(s) in the cell.

FIG. 13B shows an example of multiple tracks (labeled T0 to T7) formultiple cells 1310 to 1330 located in the same row on the chip, inwhich the boundaries of the cells 1310 to 1330 are indicated by dashedlines in FIG. 13B. In this example, cell 1320 is adjacent to cells 1310and 1310, and is located between cells 1310 and 1330.

As shown in FIG. 13B, the cells 1310 to 1330 have the same number oftracks and the same height (labeled “H”). In this example, the tracks(labeled T0 and T7) shown in FIG. 13B represent available paths forplacing metal lines formed from the same metal layer (e.g., bottom-mostmetal layer in the BEOL) in the cells 1310 to 1330. The cells 1310 to1330 may each include a metal interconnect (not shown in FIG. 13B) forgate tie-off, in which the metal interconnects of the cells 1310 to 1330are placed on the same track. Thus, in this example, the metalinterconnects of the cells 1310 to 1330 extend along lateral direction1330, and are aligned with one another in lateral direction 1340 sincethey are located on the same track. In general, metal lines located onthe same track are aligned with one another in lateral direction 1340.The metal interconnects of the cells 1310 to 1330 may be combined intoone continuous metal interconnect that extends across the cells 1310 to1330 or may be separate metal interconnects that are spaced apart bygaps in lateral direction 1330.

Each of the cells 1310 to 1330 in FIG. 13B may be an instance (i.e.,copy) of any one of the exemplary cells shown in FIGS. 3A, 3B, 4A, 4B,5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B, 9A, 9B, 10A and 10B, in which lateraldirection 1330 corresponds to lateral directions 340, 460, 560, 660 and1062, and lateral direction 1340 corresponds to lateral directions 342,465, 565, 665 and 1066. Two or more of the cells 1310 to 1330 may eachbe a separate instance of the same cell shown in one of the abovefigures.

As discussed above, any one of the exemplary metal interconnectsdiscussed above may be formed (e.g., using lithographic and etchingprocesses) from the bottom-most metal layer in the BEOL of the chip. Thebottom-most metal layer may be referred to as metal layer M0 or metallayer M1 depending on whether the designation of the metal layers in theBEOL starts at M0 or M1.

Although FIGS. 3B, 4B, 5B, 6B, 7B, 8B, 9B and 10B show examples in whichgate contacts are coupled directly to the metal interconnect, it is tobe appreciated that the present disclosure is not limited to thisexample. For example, each of these gate contacts may be coupled to themetal interconnect through a respective via disposed between the gatecontact and the respective metal interconnect.

Within the present disclosure, the word “exemplary” is used to mean“serving as an example, instance, or illustration.” Any implementationor aspect described herein as “exemplary” is not necessarily to beconstrued as preferred or advantageous over other aspects of thedisclosure. Likewise, the term “aspects” does not require that allaspects of the disclosure include the discussed feature, advantage ormode of operation. The term “coupled” is used herein to refer to thedirect or indirect coupling between two structures.

Any reference to an element herein using a designation such as “first,”“second,” and so forth does not generally limit the quantity or order ofthose elements. Rather, these designations are used herein as aconvenient way of distinguishing between two or more elements orinstances of an element. Thus, a reference to first and second elementsdoes not mean that only two elements can be employed, or that the firstelement must precede the second element.

It is to be understood that present disclosure is not limited to theterminology used above to describe aspects of the present disclosure.For example, an active region may also be referred to as a diffusionregion or another term. In another example, a power rail may also bereferred to as a power grid or another term.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples described herein but is to be accorded the widest scopeconsistent with the principles and novel features disclosed herein.

What is claimed is:
 1. A chip, comprising: a first gate; a first source;a first source contact disposed on the first source; a first metalinterconnect above the first source contact and the first gate; a firstgate contact electrically coupling the first gate to the first metalinterconnect; a first via electrically coupling the first source contactto the first metal interconnect; a second gate; a second source; asecond source contact disposed on the second source; a second metalinterconnect above the second source contact and the second gate; asecond gate contact electrically coupling the second gate to the secondmetal interconnect; a second via electrically coupling the second sourcecontact to the second metal interconnect; wherein each of the firstmetal interconnect and the second metal interconnect extends along afirst lateral direction, the first metal interconnect is aligned withthe second metal interconnect in a second lateral direction, and thefirst lateral direction is approximately perpendicular to the secondlateral direction; a third gate; and a fourth gate; wherein the thirdgate is between the first source and the first gate, the first metalinterconnect passes over the third gate, the fourth gate is between thesecond source and the second gate, and the second metal interconnectpasses over the fourth gate.
 2. The chip of claim 1, further comprising:a power rail; a third via electrically coupling the first source contactto the power rail; and a fourth via electrically coupling the secondsource contact to the power rail.
 3. The chip of claim 2, wherein thepower rail is a voltage supply rail or a ground rail.
 4. The chip ofclaim 2, wherein the first metal interconnect, the second metalinterconnect, and the power rail are formed from a same metal layer. 5.The chip of claim 2, wherein the first metal interconnect and the secondmetal interconnect are spaced apart from one another in the firstlateral direction.
 6. The chip of claim 1, wherein the first metalinterconnect, and the second metal interconnect are formed from a samemetal layer.
 7. The chip of claim 1, wherein the first metalinterconnect and the second metal interconnect are spaced apart from oneanother in the first lateral direction.
 8. The chip of claim 1, furthercomprising: a drain; and a drain contact disposed on the drain; whereinthe drain is between the first source and the first gate, and the drainextends under the first metal interconnect.
 9. The chip of claim 1,wherein at least a portion of the first gate, at least a portion of thesecond gate, the first source, and the second source are within acontinuous active region.
 10. A chip, comprising: a first gate extendedalong a second lateral direction; a first source electrically coupled toa power rail; a first metal interconnect extended along a first lateraldirection approximately perpendicular to the second lateral direction,wherein the first metal interconnect lies above the first gate and thefirst source, and the first metal interconnect is configured toelectrically couple the first gate to the first source; a second gateextended along the second lateral direction; a second sourceelectrically coupled to the power rail; and a second metal interconnectextended along the first lateral direction, wherein the second metalinterconnect lies above the second gate and second source, the secondmetal interconnect is configured to electrically couple the second gateto the second source, and the first metal interconnect is aligned withthe second metal interconnect in the second lateral direction.
 11. Thechip of claim 10, wherein the power rail is a ground rail.
 12. The chipof claim 10, further comprising a third gate extended along the secondlateral direction, wherein the third gate is between the first sourceand the second source, and the third gate is floating.
 13. The chip ofclaim 12, wherein the third gate is next to the first source and next tothe second source.
 14. The chip of claim 12, wherein the first metalinterconnect and the second metal interconnect are spaced apart from oneanother in the first lateral direction.
 15. The chip of claim 10,wherein the first metal interconnect and the second metal interconnectare in a bottom-most metal layer of back end of line (BEOL).
 16. Thechip of claim 10, wherein the power rail is extended along the firstlateral direction.
 17. The chip of claim 10, further comprising: a thirdgate; and a fourth gate; wherein the third gate is between the firstsource and the first gate, the first metal interconnect passes over thethird gate, the fourth gate is between the second source and the secondgate, and the second metal interconnect passes over the fourth gate. 18.The chip of claim 17, wherein the third gate is next to the firstsource, and the fourth gate is next to the second source.
 19. The chipof claim 17, wherein the third gate and the fourth gate are not dummygates.